1. Field of the Invention
This invention is directed to apparatuses and methods for wellbore operations and to installation and production apparatuses and methods.
2. Description of the Prior Art
Often deficiencies occur in producing oil and gas wells, either because of problems with the various production mechanisms or because of depletion of the natural resources produced from the well. The processes, methods, and equipment used to return deficient wells to production are referred to as "workover" services and "workover" rigs.
In a typical problem situation, a well which has "sanded up" (i.e., sand has infiltrated the production zone and production tubing) and is off production must be repaired so that production can be resumed. The workover of such a well can include the following:
1. Workover rig is moved to location and prepared for work.
2. Blowout preventers are installed.
3. Production tubing present in the well is removed.
4. A working string is run into the hole and sand is washed from the well.
5. Working string is removed from the hole.
6. A bridge plug is set above original perforations and production zone to seal them off.
7. Casing is tested for leaks and repaired if necessary.
8. Casing is perforated above bridge plug and perforations are washed.
9. New production zone is gravel packed.
10. Production tubing is run into the hole and production packer is set.
11. Blowout preventer is removed, production tree is installed and workover rig is removed. Such a workover procedure is complex, expensive, and time-consuming.
In the typical method used to produce a well (whether it is deficient or not) complex and expensive steps are required, including multiple trips into and out of the wellbore. For example, production of a well using a conventional through-tubing gravel pack and crossover tool requires the following:
1. Run in the string with the crossover tool and screen assembly.
2. Pump gravel pack sand through the crossover tool and around screen assembly.
3. Remove the crossover tool.
4. Use a wireline to run in a wireline pack-off and a holddown assembly to isolate a zone.
The gravel packing of a through-tubing filter assembly such as a screen device often results in the sticking of the wash pipe in the screen of the filter assembly. Both formation sands and workover fluids containing dirt or other solids can exacerbate this problem.
Wireline pack-off and hold down assemblies are complex mechanisms and they cannot be tested once they are emplaced in the wellbore. If they fail, formation sand is produced up and around the screen. This can eventually result in the sanding-up of the well and prevention or inhibition of production flow. To remedy these problems the downhole equipment and filter media must be removed from the wellbore and the installational procedure must be done again.
Once an existing production zone is sanded-up, it is typical to employ a full workover rig to remove all the in-place equipment. Such workovers are very expensive. Through-tubing gravel packing presents the problems of close tolerances for pumping through crossover tools and the sticking of wash pipes.
Coil tubing units have previously been used to wash sands out of a wellbore and to jet a well in to reduce the hydrostatic head of fluid on the formation allowing production to be commenced.